1. Field of the Invention
The invention relates to a method and apparatus of recording compression encoding tables and, more particularly, to a method and apparatus of recording compression encoding tables in a pseudo read-only memory.
2. Description of the Related Art
Given the great progress made in information technology, users nowadays may store nearly any kind of data in a digital manner. In addition, owing to the rapid development of the Internet, users of today may send, and exchange, data via the Internet. However, despite the dramatic improvements in them, the data-storage technology and the network technology are often inadequate to cope with the ever-increasing data. For instance, data of images and sounds are so voluminous that it takes considerable storage space and the network bandwidth to directly store or transmit image data or sound data on the Internet. Hence, data nowadays are mostly stored by means of compression encoding in order to minimize data without deteriorating the audiovisual quality, for the sake of saving storage space and the network bandwidth.
Take audiovisual data as an example, MPEG (Motion Picture Experts Group), MP3 (MPEG Audio Layer 3), and WMA (Windows Media Audio) are the video, audio compression formats popular with users of today, thus video data and audio data are transmitted on the Internet in these file formats. It is necessary to decode whatever audiovisual data processed previously by compression encoding when the audiovisual data is to be read or played. The decoding process can be executed by either software or hardware. However, it is the central processing unit (CPU) of the system that will execute the whole decoding operation whenever the decoding process is executed by software. The drawback is that, if the system is inefficient, audiovisual quality will worsen, leading to playing troubles, such as video frame skipping or audio unevenness. Conversely, such a problem is uncommon during the decoding process executed by hardware.
It is necessary to record the corresponding compression encoding tables to ensure that the decoding process yields data consistent with the previously compression-encoded data regardless of executing compression encoding or decoding by software or hardware. If the decoding process is to be executed by hardware, it will be feasible to store the compression encoding tables in a read-only memory (ROM) as well as to read their data for the sake of decoding. For instance, the compression of audio data in a WMA format involves using six types of compression encoding tables, namely huffman-RLC-16-mono, huffman-RLC-16-diff, huffman-RLC-440-mono, huffman-RLC-440-diff, huffman-RLC-44Q-mono, and huffman-RLC-44Q-diff. It requires a total of 4438×16 bits to store these compression encoding tables in the read-only memory. As regards practical integrated circuits, these compression encoding tables occupy a relatively large area of a silicon chip, making the integrated circuits large and increasing the cost of raw materials.
In short, the problem that should be addressed urgently is that the aforesaid compression encoding tables should be efficiently recorded in a read-only memory, so as to reduce the area of the silicon chip for storing the compression encoding tables and thus cut down the raw material cost.